Current practice in dentistry includes the application of composite bonding materials onto teeth for various purposes such as reshaping and recoloring.
The composite material is generally composed of a resinous substance which is polymerized in situ and which provides a hard bearing surface which has the natural appearance of a normal tooth.
The development of composite restorations of tooth color represents one of the major advances in dentistry in the past twenty-five years and has revolutionized the profession from an aesthetic concept. The use of composite material in conjunction with the evolution of light activation with it's capability of controlling setting time and the dentist's ability to etch the enamel of the teeth and thus bond the composite material directly onto the tooth represents an important aspect of modern dentistry known as bonding. Bonding enables the dentist to close spaces between teeth, repair chips in teeth, cover discolorations and reshape abnormally shaped teeth.
There are three types of composite material:
A. The conventional material which is composed of 76% inorganic filler material, such as quartz or Barium glass and 24% Resin Matrix, such as BIS GMA which is the reactive product of BIS Phenol A and Glycidyl Methyl acrylic.
B. Microfill--composed of 35-55% inorganic filler--such as fumed silica and 45-65% Resin Matrix, generally BIS GMA.
C. Hybrid--composed of a "combination" inorganic filler such as both Barium glass and fumed silica as well as a resin matrix.
In using the composite material to cover discolored teeth, the dentist is constantly confronted with a choice of colorations for the bonding material which the dentist selects on the basis of visualization and expectation as to final coloration.
Sometimes a selection of bonding material is made which, when applied onto the discolored tooth and hardened in place, does not produce the desired final tooth coloration. This is because there are two variables consisting of the coloration of the bonding material and the coloration of the tooth and these are not brought into juxtaposition until the bonding material has been placed onto the tooth. The selection of the coloration of the composite material does not take into account the discoloration of the tooth onto which the bonding material is placed and frequently when the bonding material has been placed on the discolored tooth, a strange and undesired final color is obtained.